Method of and apparatus for determining area gravity

ABSTRACT

Gravity profiles are smoothed by differing smoothing intervals. Several of the smoothed profiles are then combined, or averaged, to form an averaged area gravity value. The averaged area gravity values are subtracted one from another to generate a plurality of difference area gravity values. Each of these difference area gravity values accentuates an anomaly in a different depth range.

United States Patent {72] Inventors mm, L. Lawrence Riverside, Cont:Gllert W. EIa't, Doll, Ten; John A. Lester, Dallas. Ten: Alien W.Musg'ave,

Dell-,Tex.

[2!] Appl. No. 860,117

[22] Filed Sqt. 12, I969 453 Patented A... 10. 1971 [73) AuigneeMolllOilCorporIbn cmndflplcltioaser. No. 330,413, Dee. 13,1963, inllllndoned.

[S4] ME'I'IIODOF AND APPARATUS FOR DETERMINING AREA GRAVITY 14 CHI, 12Driving 1 [$21 US. Cl. 235/181, 235161.13, 235/l64 5n 001v 7/06,

558;: 5/34, 606g ms [$01 l 'leldoiseuch zas/m,

182, I84, 153,164, 6L6; 340M725; 324/IO [56) Relerences Cited UNITEDSTATES PATENTS 2,80l,794 8/1957 Garvin et a]. 235/616 2,959,35l l l/l960Hamilton et al. 235/153 3,112,397 ll/l963 Crook 235/l8l 3,256,480 6/1966Runge et al, 324/l0 3,284,763 ll/l966 Burg et a]. 235/l81 X 3,3 [9,2265/1967 Mott el al. 235/164 X Primary Examiner- Malcolm A. MorrisonAmlrlant Examiner-Felix D. Gruber ABSTRACT: Gravity profiles aresmoothed by differing smoothing intervals. Several of the smoothedprofiles are then combined, or averaged, to form an averaged areagravity value. The averaged area gravity values are subtracted one fromanother to generate a plurality of difference area gravity values. Eachof these difference area gravity values accentuates an anomaly in adifferent depth range.

PATENTEDAUBIOIQH 3,596,980

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METHOD OF AND APPARATUS FOR DETERMINING AREA GRAVITY This case is acontinuation of application Ser. No. 330,413 filed Dec. 13, I963, nowabandoned.

This invention relates to a method of and means for transforminggravitational potentials obtained over selected areas into forms whichaccentuate anomalies and provide information as to the depths of thestructures giving rise to them.

In accordance with application Ser. No. 669,3 l4 filed Sept. 20, 1967which is a continuation of Ser. No. 214,973 filed Aug. 6, 1962 and nowabandoned, for Method and Means for Treating Gravity Profiles," filed byone of the joint inventors of this application, gravity profiles aretreated with a plurality of selected averaging operators and differenceprofiles generated by subtracting one from the other in a predeten minedmanner. While the treatment of gravity profiles as disclosed in saidapplication has proved advantageous in revealing the nature and depth ofmasses giving rise to gravity anomalies, something has been left to bedesired. More particularly, these anomalies are generally not isolatedsymmetric masses, but rather are elongated and of changing width.Therefore, the area, extent and trends of these anomalies are notimmediately evident by comparison of profiles, whereas a study on anarea basis does disclose these features.

Accordingly, by utilizing the gravity values at all observation stationson a gravitational map and including interpolated values when needed fordeveloping a plurality of additional gravitational maps each havinggravity values averaged over a different selected area, maps ofdifference values may then be developed which will better displayanomalies due to the masses of the character above mentioned.

In accordance with the present invention, the information from which thegravity map has been drawn is treated in a manner greatly to enhance theidentification of the anomalies, not only to make them more readilyapparent, but also to yield additional and more definitive informationfrom them.

The foregoing and other objects, features and advantages of the presentinvention will be better understood from the following more detaileddescription in conjunction with the drawings in which:

FIG. I shows an untreated gravity map;

FIG. Ia shows a flow sheet of the process of the invention;

FIG. 2 shows a set of averaging operators;

FIG. 3 shows a gravity map which has been treated in accordance withthis invention;

FIG. 4 shows a gravity profile;

FIG. 5 shows a portion of the analog equipment used in practicing thisinvention;

FIG. 6 shows another portion of the analog equipment used in practicingthis invention;

FIG. 7 shows still another portion of the analog equipment used inpracticing this invention;

FIG. 8 represents all of the analog equipment used in practicing thepresent invention;

FIG. 9 is a schematic showing of digital data processing used inpracticing the present invention;

FIG. I0 shows punched cards on which gravitational data is punched;

FIG. ll shows in more detail the digital data processing used inpracticing the present invention.

Referring now to the drawings, there has been illustrated in FIG. 1 agravity map typical of those made in the field for the determination ofgravity anomalies from which information can be gained as to the natureand character of subsurface masses giving rise to them.

In the following description, reference will be made to gravity valuesappearing on the map of FIG. I and on other selected portions thereoflater illustrated, it being understood, of course, that the gravityvalues themselves are of prime importance. The gravity values also maybe utilized directly in accordance with the following explanation fortheir modification and treatment in digital form.

There has been illustrated in FIG. 2 a set of averaging operators, eachdefinitive of a selected and different area. and each symmetrical abouta common point. Thus, each averaging operator. taking into account aselected area of the surface, will provide better information as to thenature and character of the masses giving rise to gravitationalanomalies.

The first operator is designated r---| MM) 7, V hich is to be read asthe average value at a point .r,y of the gravity 3 measured over asquare 21 on each side and centered about the point any). Similarly, theremaining operators Mm) represent average values of gravity at the samepoint x, y but in respect to larger squares the respective sides ofwhich correspond to 41, IT and 161. For each operator, T is taken as theseparationdistance between rows and columns of equally spacedobservation points of the gravity potential along the periphery of theaveraging area which, in each case, is shown as asquare in FIG. 2.

A derivation of these operators will be described in substantial detailsubsequently. At this point, one need only appreciate that the operatorsmay be obtained by first individually integrating with respect todistance all gravity profiles for the particular operator square. Theintegrated values for the profiles are then divided by the distance ofthe square side.

The small circles of FIG. 2 identify the gravity values and in somecases. these may correspond with observation points, though in FIG. 1these points have been omitted. In most cases, the map of FIG. I willhave provided a grid on which the points will be spaced as rhown in FIG.2 and in respect to which there will be provided gravity values, thoughinterpolated from the actually observed gravity potentials, if necessa-It will be observed that the gravity values represented by the smallcircles on the averaging operators of FIG. 2 may be identified by theseveral rows numbered on the y-axis respectively l--l7 and the columnsalong the .x-axis identified respectively as A-().

As already explained, the operator l l a( I means that the values ofgravity lying on the periphery of and within a square whose sides are 2Tlong and including the symmetrical point L9 will be averaged together toprovide a single value of gravity potential. The operator l" 'l a (m) w,to the tight until the outer boundary of the averaging operator 11!)coincides with the right-hand limit of the gravity map. The operator isthen shifted in discrete stepsdownwardly from its first location at I,to a new location at l,I0, and the foregoing operations repeated untilthe whole map has been covered, i.e., until the lower boundary of theaveraging operator F' 1 ml) coincideswiththebottornedgeofthe map.

In FIG. I the boundary lines have been provided for convenientreference, it being understood that the map itself willbecoll'derablylargerandthatonlyasignificantportionhas been illustratedin relationtoFlG.3latertobedeecribed.

It istobe understood thatuponcornpletionofthe scanning oftbe map withthe averaging operator l i 00ml) as first described, there will beobtained new values of the gravity potential from which a new map may bedrawn.

The foregoing operations are then repeated in succession 4T 8'1 161'flay) The subtraction will be point by point and a new map developedtherefrom.

The striking results of the technique thus far explained will beapparent by reference to the fractional map of FIG. 3 where the gravitycontour lines for the corresponding area of FIG l have significantlydifferent values, and more importantly, where the gravity anomalies areprominently displayed. Thus, for example, three positive gravityanomalies A, B and C appear. For anomaly A, the inner contour line has agravity potential of +6, with successive contour lines decreasing tozero, and outwardly therefrom additional contour lines have negativevalues. Such contour lines do not appear on the map of F I6. I for thereason that the gravity potentials represented by the contour lines onFIG. 3 have, in the map ofFIG. I, been obscured by shallow and strongergravity anomalies.

As will be later explained, the masses giving rise to the anomalies A, 8and C, FIG. 3, are known to occur at depths between 12,000 feet and24,000 feet. since the map of FIG. 3 resulted from the subtraction ofthe data from the averaging operator IGT l" l g 32 from the dataobtained utilizing the averaging operator 0( v) For convenience, thedepths which will give rise to corresponding anomalies on other mapsresulting from the four operations with the four operators of FIG. 2 areas follows:

2T 0 to 3,000 g( ,y) am y) 2T 4T 3,000 to 6,000 00:, y) 00:, :1) 4T 8T6,000 to 12,000 r r't May) 9( 0) 8T 16T 12,000 to 24,000 r\ 1nexplaining the manner in which the foregoing operations are accomplishedin analog computing equipment, several Figures will be utilized, each inpart duplicating equipment of an earlier Figure. There will then bepresented a block diagram illustrating the manner in which the number ofcomponents in the analog equipment may be decreased. The switchingfunctions unduly complicate an understanding of the operations which maybe more simply explained by using separate Figures of the kind justdescribed. Finally, there will be presented techniques for a digitalexecution of the present invention.

Referring again to FIG. I, it will be observed that there has beenmarked thereon a line 20 representative of a traverse across the gravitymap. on this line the small circles indicate gravity stations separatedby the distances T at which values of gravity have been measured orestablished as by interpolation as explained above. If, now, the gravitypotentials at each of the stations on the line 20 be plotted, a curve,such as that illustrated in FIG. 4 will be obtained, where the firstgravity value will correspond with the station A,9 and the final valueon the traverse line at Kl(,9.

As explained in the aforesaid application Ser. No. 2 l4,973 to Lawrencethe interval T between stations is chosen to be less than one-half thelength of the shortest fluctuation in the observed gravity potential,i.e., the distance between the beginning and end of the shortest anomalyas measured along the abscm. In one embodiment of the invention thedistance T was selected as 3,000 feet. Though the averaging operators inaccordance with the present invention are in terms of area, it isconvenient to show these operators for the line or gravity profile 20and they have been illustrated as 2T, 4T and 81 for profile 20. It is tobe understood that there will be a plurality of profiles extendingacross the map of FIG. 1, each spaced vertically from the otherpreferably by distances equal to the spacing between the stations ofprofile 20, i.e., about 3,000 feet. To minimize the number of referencecharacters on FIG. I, only a few identifying characters have beenutilized. Thus, for example, the first column A has thereon the row 9identified. Thus, the first observing station for profile 20 isidentified at the point A,9. Similarly, the station located at thecenter of the averaging areas may be identified as I,9. Finally, it willbe noticed that the illustrated part of the map terminates atapproximately the row VV. If all of the rows of the columns were to belabeled, they would appear in the same way as the rows and columns havebeen identified on the averaging operators of FIG. 2 except that theywould be extended to cover the gravity map of FIG. 1. Accordingly, forevery profile corresponding with the horizontal line through the rows 1,2, 3, etc., there may be provided a gravity profile corresponding withthe one illustrated in FIG. 4. These gravity profiles in turn may berepresented by amplitude signals on a magnetic tape or alternatively byamplitude signals on any reproducible medium as, for example, variablearea film, and by stored values in a digital system. The manner in whicha record may be developed on magnetic tape is well understood by thoseskilled in the art, an optical arrangement for this purpose having beendescribed in the aforesaid Lawrence application. Thus, referring to FIG.5, it will be assumed that on a magnetic drum 30 there will have beenrecorded the gravity profiles beginning with the first profile takenalong the first row I of FIG. I. There will be a pickup head l"associated with this record. Similarly, there will be additional pickupheads associated with each of the additional profiles, the pickup headsP P, and P being shown for the profiles respectively above and below row9 identified on FIG. I. A motor 3] drives the drum 30 together with atape drum 32 a third drum 33 as well as additional drums later to bedescribed. These drums are preferably of like diameter and in each casethe length of tape on the drum will be proportional to the distance onthe map of FIG. 1 from initial boundary A to final boundary VV.

In order to develop each area averaging operator of FIG. 2 there willfirst be developed individual averages for each profile. The profileswill then be averaged together. Finally,

differences will be taken to provide the information for the newdifference maps which can then be plotted on an areaaveraged basis.

Assuming now that the motor 3] has been energized to initiate rotationof the drums 30, 32 and 33 at the beginning of the record, it will beobserved that pickup head P, will apply to an amplifier 34 signalsrepresentative of the gravity profile spaced just above the profile 20on the map ofFlG. l. The output from the amplifier 34 is applied to anintegrator 35 and, through a recording head 36, is recorded on the drum32. This drum 32 has associated with it two pickup heath 37 and 38spaced apart from a reference point 39 by distances equal to Tcorresponding with the separation distances between each ofthe stationsillustrated in FIG. I and also in FIG. 2. The pickup head 37 has beenindicated as being spaced from the reference point 39 by the value +Twhile the pickup head 38 is spaced from the reference point by theamount 'I, this being the correct notation with drum rotation asindicated by the arrow. The signal on drum 32 corresponding with fg(t)dr will be first applied to an amplifier 40 and thence through aresistor 41 to a summing amplifier 42. As the record arrives at thepickup head 38, signals representative of the gravity profilewillbeapplied toan amplifier and thenoebywayof resistor 44 to theamplifier 42. It will be noted that the polarity of the inputs toamplifier 42 are of opposite sign; that from the amplifier 40 beingnegative and that from amplifier 43 positive. The opposing polaritiesare readily obtained by reversing the connections to one amplifierrelative to those to the other and as applied to the summing resistors41 and 44. The signal applies by way of summing resistor 41 may berepresented as I g(l+T)dr and the signal applied by way of summingresistor maybe represented as /g(t7')dt. lnasmuchasit isdesiredtogenerate an output signal which is independent of the length of theoperator, the output signal from the amplifier 42 is divided by thelength of the operator, in the present case, 2T. Accordingly, theresistor 45 will have its tap or movable connection set at a valuerepresentative of l/2T). In this connection, the distance between theheads 37 and 38 corresponds with the value of 21. That distance will, ofcourse, be proportional to twice the spacing of the observing stationsappearing on the map on FIG. I. The output of the amplifier 42 alter thedivision just described is applied by way of a switch 47 to a recordinghead 48 associated with the drum 33. Thus, there will be recorded ondrum 33 the profile detected by the pickup head P, after averaging bythe operator 2T.

After the completion of the foregoing operations, the drum 30 will havebeen returned to its initial position. At this time, the switches 34aand 47, preferably ganged together, are moved to the next left-handpositions, i.e., to connect the pickup head P, to the amplifier 34 andto connect the output from the dividing resistor 45 to the nextrecording head 49. The second operation will be identical to that justdescribed and as the drum 30 completes another revolution the switches34a and 47 will again be stepped to the left until there will have beenscanned the multiplicity of profiles recorded on the drum 30 and theavenge values of each over the interval 21 recorded on the drum 33.

Assuming now that there have been recorded on the drum 33 the averagedprofiles with the averaging operator 21', it will be understood at oncethat the pickup heads P,', P. and P,.,' can reproduce continuously theaveraged profiles. ll, now, these three averaged profiles are averagedtogether, then a consideration of area is introduced. More specifically,and referring to FIG. 2, there will have been recorded on the drum 33the average values for a profile corresponding with the points H8, [8and J8. Similarly, there will be corresponding averages for points onprofiles 9 and at H, l and J. It, now, these profiles be averagedtogether, there will be obtained the average area-gravity potential l' lemu) across the map for the strip between H and J. The manner in whichthe average values as reproduced by pickup heads P., P. and P areutilized to accomplish the foregoing results will now be described inconnection with FIG. 6 where the drums 30 and 33 have again beenillustrated but with drum 32 omitted. in this Figure as well as in thearrangement of FIG. 5, the pickup heads associated with drum 33 arelocated in the same relau'onship in the record as are the pickup headsassociated with drum 30. The reason for this will soon be made apparent.The pickup heads P.', P, and P,, are connected by a gang switch 50respectively to summing resistors 51. 52 and 53 of a summing amplifier54. Inasmuch as average values are desired, the resistor 55 has itsassociated contact or tap set at a value to divide the output of theamplifier 54 by three. In some instances, it may be desirable to recordthe average values obtained in the manner just described and an outputterminal 57 connected to output conductor 58 may be provided forconnection to a recorder of a kind later to be described, or it may be arecorder of the continuous type as illustrated in FIG 7 of said Lawrenceapplication.

The average gravity values obtained at the output conductor 58 areapplied by way of a summing resistor 59 to a summing amplifier 60. Asindicated by the and signs, the polarities to this summing amplifier arereversed, the signal from summing resistor 59 being negative. The otherinput to summing amplifier 60 is obtained from pickup head P, of drum30. Alter amplification by amplifier 34 the signal is applied throughthe summing resistor to the amplifier 60. Thus, there has beenillustrated the manner in which there is obtained the operation inasmuchas there has already been described the manner in which the areaaveraging operator moves across the traverse of the map in discretesteps, there will now be explained how the system of FIG. 6 achievesreadout of the desired information.

The output of amplifier 60 is applied to the input of amplifier 61forming a part of a self-balancing measuring system and including amotor 62 operable in one direction or another proportional to themagnitude or phase of the output from amplifier 60. Such an arrangementof amplifier and motor is well understood by those skilled in the artand has been discussed in U.S. Pat. No. 2,l [3,164 to Williams. Themotor 62, through its shaft 620, drives a plurality of print wheels 63printing digits 0-9 and together forming a printer mechanism forapplying to a chart 64 digits relative to the magiitude of the output ofamplifier 60 and proportional to the quantity Counting mechanismsincluding print wheels are well known to those skilled in the art. Theprint wheels 63 are driven in succession one after the other by theshaft 62a and are suspended on a carriage 65 positioned along the chartby means of a violin string 66 suspended on pulleys, one of which isdriven by a driving pulley 66a. The drive for pulley 66a comprises apawl 67a and a ratchet wheel 67b. The pawl pivoted about the support 670is operated by cam 67d driven through mechanical connection 67: and bymotor 31. The cam 67d rotates the ratchet wheel 67!: one notch for eachrevolution of the drums 30 and 33. Thus, the ratchet wheel 67b moves thestepping switch 50 to the left through one position and at the same timemoves the carriage 65 along the chart 64 by a distance proportional tothe distance T.

It is to be observed that the print wheels 63 are illustrated in spacedrelation with the chart 64. The chart 64 is held in this spaced relationby a mechanical linkage including the arm 68 which is pivoted at 68a.Arm 68 moves the chart into and out of engagement with the print wheels63 in response to movement of arm 68b which is biased outwardly byspring 68c. Arm 68b is pivoted hitting arm 68d which carried a camfollower 68. The printing operation is directly controlled by a notchedwheel 69 carrying a plurality of succeeding teeth and troughs, the tooth69a and the trough 69b pulled as the motor 31 rotates drums 30 and 33through a distance corresponding with the distance T, the wheel 69 ismoved to bring the tooth 69a beneath the cam follower 68a. Themechanical linkages 68, 68b and 68d position the chart into engagementwith the print wheels 63. When the wheel 69 rotates further so that thetrough 69b is behind cam follower 68b, the chart is moved out ofengagement with the print wheels. The chart 64 is likewise driven by wayof the mechanical connection 67e. The chart 64 has been shown as endlessand its length will be proportional, preferably equal, to the length ofthe gravity information stored on circumferential track of the drums 30and 33.

For details of the print operating mechanism, only diagrammaticallyillustrated in FIG. 6, reference may be had to US. Pat. No. 2,080,065 toRoss et al. wherein instead of a print wheel, the carriage support andoperating mechanism therefore have been illustrated as applied to achart marker in the form of a pen. With the above understanding of theareas of the readout mechanism, a brief resume of the operation may behelpful. With the gravity records on drums 30 and 33 in their initial orzero positions in respect to the pickup heads it will be remembered thatthe chart 64 will likewise be in its initial position and the carriage65 in its left-hand position. Accordingly, the print wheels 63 willprint in succession with spacings therebetween equal to T the gravityvalues as determined at the output of amplifier 60 and as referred to inFIG. 1 across the first and uppermost row. The operation, of course, iscontinuous until there will have been recorded gravity values which maybe held positive or negative as shown in FIG. 3 and of the same ordiffering magnitude. After a single revolution of drums 30 and 33 and ofchart 64, the gang switch 50 is operated and the carriage 65 is steppedto row 02 of FIG. 1 and the operations are repeated, and it is in thismanner that there is produced on the chart 64 the gravity values foreach station. By merely interconnecting points of equal value the equalgravity lines may be drawn to delineate the gravity patterns asillustrated in FIG. 3.

It will now be seen that there has been provided an arrangement in whichthe operator has been moved from the left-hand side of the map, FIG. I,to

the right-hand side thereof and the manner in which the average valuesof gravity taken over the area represented by that operator have beenread out and recorded as discrete values of gravity potential.

It will be understood that the foregoing operations are again carriedout with a change in position of the operator by one unit T as from A,9to A,l on the map of FIG. I. This is done by shifting the gang switch 50one space to the left. By successive cycles of operation, correspondingwith the multiplicity of traverses across the map, there will begenerated a new set of gravity values by means of which there may beplotted a map corresponding to the foregoing function If gravityanomalies appear on the map, for example, the kind already described inconnection with FIG. 3, it will be known that the masses giving rise tothem will be at relatively shallow depth as, for example, from 0 to3,000 feet. It will be understood, of course, thatthis range of depth.and those'earlier discussed are applicable to the examples utilized forexplaining the invention. Different ranges will be associated withdifferent intervals ofT.

What has been described thus far has been the steps involved ingenerating the function 2 T ly) my) As already stated, a map of thisfunction provides useful information regarding anomalies falling in thedepth range of 0 to 3,000 feet.

There will now be described the manner in which the funcis generated. Byplotting values of this function on a map, useful information regardinganomalies falling in the depth range of 3,000 to 6,000 feet may beobtained. Referring to FIG. 7, the drums 30, 32 and 33 are again shown.It will be remembered that drum 33 has recorded thereon, in successivetracks, the gravity profiles along the rows l--l7, FIG. 1, averaged overthe interval 2T. More particularly, the drum 33 has recorded on thetrack under the pickup head P the gravity profile along the row 8, FIG.I, averaged over the interval 2T; under the pickup head P, the gravityprofile along the row 9 averaged over the interval 2T; and under thepickup head P the gravity profile along the row 10 averaged over theinterval Also shown in FIG. 7 is the drum 70 which has recorded thereon,on successive tracks, gravity profiles recorded along the rows l-l7,FIG. 1, and averaged over the interval 4T, The manner in which thegravity profiles have been averaged over 4T is as follows.

The gravity profile along the row 8 has been recorded on drum 30 underthe pickup head P,. This gravity profile signal is sensed by pickup headP amplified at 34, integrated at 35 and recorded on drum 32. Thisintegrated gravity profile is picked up on drum 32 at the pickup head71. The signal from pickup head 71 is amplified by amplifier 72 andconnected through summing resistor 73 to an amplifier 74. The profilerecorded on the drum 32 is also picked up by a pickup head 75 spaced byan interval 2T on the other side of the reference mark 39. It will benoted that the pickup heads 71 and 75 are spaced from one another by aninterval 4T. The profile from pickup head 75 is amplifier by amplifier76 and applied through summing resistor 77 to the amplifier 74. Thesignal from amplifier 76 is of opposite polarity to the signal fromamplifier 72. As explained above, the output of amplifier 74 afterdivision by four by the voltage divider 45 a will be proportional to thegravity profile along the row 8 averaged over the interval 4T. Theoutput of amplifier 74 is connected through stepping switch 78 to thepickup head 79 which records the averaged gravity profile for the row 8,FIG. I, on a track of the drum 70. The gravity profile along the row 9is next averaged over the interval 4T and recorded on the drum 70 asshown, the stepping switch 340 having been moved to the left to pick upthe signal from pickup head P,. This signal is averaged over theinterval 4T by means of the drum 32, summing amplifier 74 and voltagedivider 45a, as described above. The stepping switch 78 is moved to theleft one position so that the profile along the row 9 is recorded at thepickup head 80 on the drum 70. In a similar manner, the profile alongthe row It] averaged over the interval 4T is recorded by the recordinghead 81; the gravity profile along row 6 averaged over the interval 4Tis recorded by recording head 82 and the profile along the row 7averaged over the interval 4T is recorded by recording head 83.

The five recorded tracks referred to above are picked up by therecording heads 84-88. The five picked-up signals are connected throughthe stepping switch 89 and the summing resistors 9I95 to the input tosumming amplifier 96. The output of summing amplifier 96 is connected tothe voltage divider 97 which divides the output of amplifier 96 by afactor of 5. The signals appearing at the tap 98 are equal to theaveraged values of the five gravity profiles recorded on the drum 70.The signal appearing at the tap 98 is the function Way) I This signal isapplied through resistor 99 to one input of a summing amplifier I00. Thesignal proportional to other input to amplifier I00. The output ofamplifier I is proportional to By moving stepping switches 34a, and 89to successively different left-hand positions, the functions r'"| l l00m!) way) will be generated in succession for each gravity profile.These functions can be plotted in a manner similar to that shown in FIG.3 to produce a map which accentuates the anomalies falling in the depthrange of 3,000 to 6,000 feet.

There has now been described in detail the manner in which the functions2T 2 T 4 T are generated. There will now be described the manner inwhich the functions l l and l l I 90m!) 90 ,11) 00 ,11) 00 4/) aregenerated. FIG. 8 shows a complete analog computing system of the typerequired to generate all of the desired functions. To simplify thedescription, FIG. 8 is somewhat diagrammatic in that many of theamplifiers, stepping switches and averaging voltage dividers have beenomitted. However, the inclusion and connection of these circuitcomponents can readily be ascertained by comparing FIG. 7, showing allof these circuit components in detail, with that portion of FIG. 8 whichrepeats the showing of drums 30, 32, 33 and 70 but omits the detailedcircuit components.

Gravity profiles averaged over the interval 81 are produced at theoutput of summing amplifier I01 and recorded on drum 102. Nine of theseprofiles are averaged in amplifier I03, the output of which isproportional to the function |-1 (m) a As before described, the functioncan be generated for all gravity profiles on the map shown in FIG. 1.This value is subtracted from the function Mm) in the amplifier I04 toproduce the function 00ml) 9 (m) This function can be plotted to form amap which accentuates anomalies falling in the depth range of 6,000 to12,000 feet.

In order to generate the function any) Way) the drum I05 is provided.The signals proportional to gravity profiles averaged over the intervalI6T are obtained from summing amplifier 106. These gravity profiles arerecorded on the drum I05. Seventeen of the profiles recorded on drum I05are picked up simultaneously and averaged in the amplifier 107. Theoutput of this amplifier, proportional to |--1 9 ,11) is applied toamplifier I08. The function l 0 (w) is subtracted from the function r005.11) by the amplifier 108. The function ml) slay) can be obtained forall of the gravity profiles on the map shown in FIG. 1. The functions r1 r-1 was) 90 .11) for the map of FIG. I are plotted in FIG. 3. The mapof FIG. 3 accentuates the anomalies falling in the depth range of 12,000to 24,000 feet.

There has been described the manner in which a gravity map of the typeshown in FIG. I has been transformed to a map of the type shown in FIG.3 by analog techniques.

There will now be described the manner in which the gravitational datais treated digitally on an area basis to produce a map such as shown inFIG. 3. In FIG. 9 there is shown a diagrammatic representation of a dataprocessing system. This is a representation of most commonly availabledigital data processing systems which include an input-output units foraccepting input data 121 and for producing as an output reportsindicated at 122. The digital data processing system operates undercontrol of instructions 123 which are fed into the computer throughinput-output units I20. External data 121 and instructions 123 arestored in the computer internal storage unit 124. These data andinstructions are processed by arithmetic unit 125 under control of thecontrol unit 126 which operates in accordance with instructions 123.

There will now be described a particular digital computer which can beused in digitally processing the gravitational data. However, it will beunderstood that the input-output units 120, internal storage unit I24,arithmetic unit 125 and control unit 126 can take many forms apart fromthose to be subsequently described.

In the computing system to be presently described, data I21 andinstructions 123 are punched onto cards such as those shown in FIG. I0.These cards are prepared by an operator at a card punch. The operatorprepares a card similar to the ones shown in FIG. 10 for each of thegravitational profiles on the map of FIG. I. As an example, the card 127will be punched to represent the gravitational values along row 9 ofFIG. 1. Each of the vertical columns on the card is a digital coderepresenting the gravitational potential at a particular station alongrow 9. For example, the vertical column 128 contains a punched digitalcode representing the observed gravity at the station A,9, FIG. 1.Vertical column I29 contains a punched digital code representing theobserved gravity at the station B3 and so on. The observed gravityvalues for each of the rows I-17 are punched onto cards similar to thoseshown in FIG. I0. Cards containing the gravitational information arestacked in the card reader 130, FIG. 11. Any commercial available cardreaders may be used for this purpose, the card reader commerciallyavailable as IBM Model No. 522 is one of many suitable for this purpose.As the cards are read, the codes are translated in the translator I31 toa code which is usable by the computer. Translator l3! converts eachcard code to a code which is usable in the magnetic drum computingsystem shown in FIG. II. The commercially available IBM 650 MagneticDrum Computer is suitable for use as the computer illustrated in FIG.II.

Before describing the manner in which the computing system shown in FIG.II operates on the gravitational data toproduceamapsuchasshowninFlG.3,therewillbe described several operationalfeatures of the computing system. An understanding of the operation ofthe computer in executing the following stored instructions is necessaryto understand the techniques used to prooem the gravitational data:

L'I'heinstruction IICI OOOusedtonarnferdatafromthecardreadertothestoragelocatimoraddremesininternal storage of thecomputer;

2. Theinstmction ADDOOOandsimilar inatructionsusedto performarithmetical operation on data stored in internal storage;

3. 'IhelnatructionsSlS000,ClS 008,.IMP06I and otherinstructiona used inperforming at indexing cycle;

4. The instructions PNI OOOandCSP 001 used in printing out the computedgravitational values.

The performance of the foregoing imtructiom described in conjunctionwith the following short description of the data processing system shownin FIG. I I.

The codes from translator 13] are stored in one of the storage locationson magnetic dnrrn I32 in response to, for example, the instruction RC!001 This instruction haanoperation code portion (Op. Code) RC1specifying that the next cardincardreader IBBistobereadndanaddrQportion, 00l,specifyingthatcodesfromthecardaretobestoredinconsecutive storage locations on magnetic drum I32 beginning at storagelocation OOI.

Magnetic drum I32 includes a plurality of quick access bands, the quickaccess bands I ,2 It] being shown and a plurality of main storage bands,the main storage bands I, 2, 3 being shown. The input codes are storedin particular storage locations on the magnetic drum I32 under controlof the head switching control circuit I33. Head switching circuit I33'a, in turn, responsive to the address portion ofthe instruction storedin address register I340.

Each band on magnetic drum 132 is divided into many unit areas per inch,each of which stores a bit. A magnetized area represents a i; anunmagnetiaed area represenu a 0. Each code from translator I31 can beput into one bit position on a hand We will assume that all of the codeson a card can be recorded on one band. Each band on magnetic drum 132will be assumed to contain 80 storage locations. Therefore, main storageband I contains the storage locations l-80, main storage band 2 containsthe storage locations 8l--l60, main storage band 3 contains the storagelocations l6l240, and

so on.

The codes are transferred to and from storage locations on magnetic drum132 under control of the control unit 134. The control unit I34 includesan instruction register 135 which stores an instruction to be executed.Each instruction to be executed includes an address portion and anoperation portion. The address portion of the instruction is set intothe address register 134a as previously mentioned. This address register[340 controls the storage location on magnetic drum 132 from which thecode to be operated on is transferred.

The operation portion of the instruction register 135 is decoded bydecoder I36 which controls many functions including the operation to beperformed by arithmetic unit 137. When the operation has been performedby arithmetic unit I37, the arithmetic unit I37 advances the instructioncounter I38 by one count to indicate the present instruction has beenperformed and that the next instruction can be called up from memory tobe performed.

The operation of the control unit I34 and the arithmetic unit I37 rsbest illustrated by describing the operation in conjunction with theperformance of a simple instruction. As an example, the instruction ADD268 that is stored in storage focation 062 will be performed. Thisinstruction means that the contents of storage location 268 are to beadded to the contents of the accumulator I39 in the arithmetic unit. Theoperating cycle can best be described as consisting of seven steps. Theseven steps are listed below and the associated numbers are indicated onthe drawing as circled numbers on the data flow and control lines whichperform the step. The steps in the performance of the instruction ADD268 are as follows:

1. Transfer the operation part of the instruction, ADD, from theinstruction register to the decoder I36.

2. Transfer the address part of the instruction, 268, from theinstruction register 135 to the addres register I340.

3. Copy into the arithmetic unit 137 the operand (which may be eitherdata or an instruction) located at address 268.

4. Execute the required operation, ADD, in the arithmetic unit. Notifythe control unit when the operation is executed.

5. Increase the number 062 in the instruction counter I38 by l, to 063,to indicate the address ofthe next instruction.

6. Transfer the number 063 from the instruction counter I38 to theaddress register 1340.

7. Get the instruction, SUB 495, located at address 063 and put it intothe instruction register.

In order to make the most efficient use of programming time and the useof storage for instructions, and indexing cycle is provided for in thedigital computing system. An index register I40 together with comparatorI41 are used to change a singleinatructionsothatitcanbeusedoverandoveragainto carry out a program of instructions. The operation of the indexregister I40 and comparator I41 in performing an indexing cycle is bestillustrated by the following example. Assume that it is desired to addtogether the contents of three storage locations 068, 069 and 070 and tostore the result in storage location 07L The easy way to perform thisoperation would be to insert the following instructions in sequence inthe program assuming that the program is starting with the instructionstored in location 0.60:

Instructions Address Op. Code Address 060 ADD 068 06l ADD 069 062 ADD070 063 S'I'A 07! In carrying out this simple program, the computerwould remove the instruction ADD 068 from storage location 060 andinsert it in instruction register I35. The instruction would beperformed by adding the contents of storage location 068 to theaccumulator 139. After performance of this instruction the instructionstored in storage location 061 would be put into instruction registerI35 and this instruction would be perfonned by adding the contents of069 to accumulator I39. After performance of this instruction, theinstruction stored in location 062 would be transferred to instructionregister 135 and this instruction executed by adding the contents ofstorage location 070 to the accumulator 139. Next, the instructionstored in storage location 063 is transferred to instruction re gisterI35 and this instruction is performed by transferring the contents ofthe accumulator to the storage location 07 l While the above routine isquite straightforward when only the contents of three storage locationsare to be added together, this approach becomes quite cumbersome when agreat number of storage locations are to be added together. In order toperform this operation more simply an indexing cycle is programmed. Theabove problem would be programmed with an indexing cycle as follows:

Storage Location 7 Assuming that we begin the program With theinstruction stored at storage location 060, the instruction $18 000 isper formed by the decoder 136 acting over control line I42 to set theindex register I40 to zero. The next instruction, ADD 068 is performedby address register I340 acting over the control line I43 to gate thecontents of storage location 068 over the data flow line 144 to thearithmetic unit. The decoder I36 acts through control litre 145 to causethe number in storage location 068 to be added to the contents ofaccumulator 139.

m lnstructlms location Op code Addrea Mn 8l8 (I!) Set index register to0.

06] ADD 068 Add tosccmnulator the number stored at the address 068 pluscontents the index register 0152 INC nor Increment index register by I.

063.. ClS nos Cmnpare contents or Index register with the contents orstorage location 008 which contains the number 3. Ir contents areuneapnl, take the next instruction in pence 064; it equal, skip oneInstruction to the storage location 065.

g Jump to e instruction at storage location Stare contents otwcumulstorin storage location 071.

The nextinllructionINCOOl isperforrnedbythedecoder I36 acting overcontrol line 142 to 'mcremem index reg'lter I40 by I.

The nextinstructlonclsoollisperlonnedbythecompcator 141 which comparesthe content ofindex reg'srer I40, thecontentsnowbeingmLwiththecontentsofstoraplo-catim 008ThestorngelocationOOScontainsthenumberlSince the comparator 141indicates that the two numbers are unequal, it acts over control lineI46 to gate the next instruction stored in storage location 064 to theinstruction register.

Theinstructionstoredinltoragelocationoflisajrmpinstruction JMP on. Theinstruction JMP 061 acts through control line I43 to cause theheadswitching control circuitry I33 to transfer the instruction storedat storage locttion 061 to the instruction register. Th'u differs fromthe normal sequence of operation in which the instruction at address 065would next be transferred to imtruotion register 135.

The instruction stored at storage locations 061 is ADD 068. The contentsof the index register 140 are added to the address. portion 068. Theindex register [40 now contains a I ri when this is added to the address068, the addres is modified to 069. The contents of storage location 069are added to the contents of accumulator I39 to complete thisinstruction.

The instructions INC 00] and CIS 008 are performed as before Since thecontents of index register 140 is incremented t0 2 and since this stillproduces no comparison with the contents of storage location 008, a 3,the next instruction IMP 06l is performed. This causes a jump back intothe instruction stored at address 061 and another cycle is performed. Inthis cycle the contents of storage location 070 are added to theaccumulator. In this cycle, when the instruction CIS 008 is performed.the comparator 14! indicates a comparison. The

comparator I41 then acts over control line 146 to skip an instrucuon andto gate the instruction stored at storage location 065 to theinstruction register I35. The motion stored at address 065 is STA 07 l.Th: instruction is performed by stormg the contents ofthe accumulator instorage location 07 I.

In this manner, the contents of storage locations 068, 069 and 070 havebeen added together and the results stored at location 071. Thissequence has been performed by using indexing cycles.

The remaining component in the digital computer of FIG. II to bedescribed is the output printer indicated generally at 1Mv Digital codesfrom storage are connected switching control 133 over the data line 161to the amplifier l6ls. The digital codes are decoded by positioningmechanism I62 which rotates the shaft I62: to set the print wheelslfltotheproperpoeitioncorrespondingwiththe digital code to be printed.The manner in which digital codes are translated to rotational movementto position printing wheels is well known to those skilled in the art.

The print wheels 163 are positioned to be brought into ongagement withthe moving chart I64. The moving chart I is brought into engagement withthe print wheek I63 by means of the print control motor I70. In responseto an instruction PNl which is decoded in decoder I36, the print controlmotor ['70 will be energized and will rotate an incremental amount. Theprint control motor I70 rotates the notched wheel I71 to cause the tooth172 to engage cam follower 173 on mechanical linkage I74. When a toothof notched wheel 17] engages the cam follower I73, the mechanicallinkage is rocked forward causingtheann I75topushthemovingrecord lflimoengagement with the print wheels 163. Further rotation of the wheel 17]causes cam follower I73 to fall into a trough in the head i hecl therebydisengaging the chart 164 from print wheels I63.

Actuation of print motor I70 also rotates the moving chart I64 by meansof the mechanical connection at 176. Afier the printing of the digit hasbeen completed, the chart 164 is incremented to the next position atwhich the printing m to occur. The operation of the printer is bestdescribed in conjunction with the performance of an instruction. Assumethe instruction PN1 068 is in the instruction register I35 The addressportion, 068, is transferred to address register 1340. Addrgs register134a acts over control line 143 to set the head switching control I33 sothat the contents of storage location 068 are transferred over line 16I,through amplifier 1610 to the decoder 162. The decoder 162 sets theprint wheels 163 to tin number specified by the contents of storagelocation 068. The 0p. Code portion PNI of the instruction is decoded indecoder 136. In response to the instruction PNl the decoder 136 actsover control line 1700 to actuate print control motor 170. Print controlmotor I70 rotates the notched wheel 17] to cause the record 164 to bemoved into engagement with print wheels I63 to print the number recordedin storage location 068. Further rotation of notched wheel 171 causesthe record 164 to be moved out of engagement with the print wheels I63.Still further rotation of mechanical linkage 171a causes the movingrecord to be moved at 176 thereby incrementing the record to the nextposition which is to be printed. in making the gravitationalcomputations involved in the present inven tion. the moving record willbe incremented a distance corresponding to the distance T on the movingrecord.

The printer I60 also has provision to move the print wheels 163 todifferent columns on the moving chart. The print wheels are carried on acarriage I65 which is movable along the shaft 169 by means of the violinstring 166 which is moved at one end by the pulley I660. The pulley 166ais rotated by ratchet wheel 16'! which is held in position by theassociated pawl 167a. The ratchet wheel l67b is rotated in response tothe column control motor [77 Column control motor [77 is actuated inresponse to an instruction CSP. The instruction CS! is decoded indecoder 136 which acts over control line 178 to actuate column controlmotor 177.

When a complete column including all of the values across agravitational profile has been printed out, an instruction CSP will beprogrammed to increment the print head to the next column so thatanother gravitational profile can be printed on {the moving record I64.In the computations involved in the present invention, the print wheelwill be incremented by a columnar distance corresponding to the distanceT.

There will now be described the manner in which the digital computingsystem shown in FIG. ll operates on the gravitational data in accordancewith this invention. There will be described the manner in which thegravitational data along the profiles 8, 9 and 10, FIG. 1, are combinedon an area basis to form the function 2 T r--n al ulaw, y) Thisexpression will be computed for the profile along the row 9, FIG. I.

As previously mentioned, the gravitational data along rows 8, 9and 10,FIG. I, are punched into three cards. It will be assumed that the cardcontaining the gravitational data along the row8 is the next card in thecard reader 130, FIG. ll. lt will also he assumed that the printerwheels I63 are now positioned over a column on record 164 which willcorrespond with row 9 on the final record. The computer will thenproceed with the following program beginning with the in- Theinstruction SIS 000 sets the index register to 0. The instruction CM I00clears accumulator I39 and adds to the accumulator the number stored atthe address 100 which is the gravitational value at the first stationalong the row 8. The instructi ons ADD lOl and ADD I02 completes the sumof all gravitational valuesin E interval 21, i .e .,fgii+ 'i')drjjg(t-T) Storage location ml... Constant used in computatbn. lIIL Do.

llllL.

010 Road the next card in Card Reader 01L Read the ncxtcard in CardReader 013 Read the next card in C 3: Set Index Register to D.

egistcr. Add to the accumulator the number s Add to the accumulator thenumber stored I1 and store in 100 consecutive locations beginning ataddress 100. I1 and store in 100 consecutive locations beginning ataddress 1X). srd Reader #1 and store in It!) consecutive locationsbeginning at address 300. Cigar the accumulator and add to theeccumuJntor the number stored at the address I00 plus the contents oithe Index torad at the address l plus the contents of the IndexRegister.

at the addrms 102 plus the contents of the Index Register.

Dll'- Div ide the contmts oi the accumulator b the number stored ataddress ml.

018. 400 Store the canton of the accumulator at sddru 400 plus thecontents of the Index Register.

019... INC 001 Incremmt the Index R tar by 1.

1m. CIB 002 Compare the contents the Index Reglsur with the numberstored in location 002 which contains the number 48.

If the contents are unequal, take the next instruction; if equal, ship 1instruction.

1MP 014 Arrival at this point rum the receding com rlson means that thecycle count is not yet complete; therefore, jump o storage location 014to another try m. SIS (I!) 021.. ADD 201 026. w ADD m can. DIA (Ill 02LSTA am 028 INC m1 0D CIS one 9m 'lhse instructions are the some asinstructions 013-02), except that the blocks of data from the next twocards are being averaged over the interval 21.

032. CAL 3t!) 0%. ADD am ADD U2 IE6. DIA till 0%" STA CD 037 IN C on 089IMP 032 Oil) SIS (Ill Set Index Register to 0.

041 (AA 400 Clam- 21B accumulator and add to the accumulator the numberstored at the address 4001mm the contents of the Index cg ter.

042. ADD 500 Add to the accumulator the number storg at the address souplus the contents of the Index Register.

043 ADD 600 Add to the accumulator the number stor at the address 600plus the contents 0! the Index Register.

0 PIA 001 Divide the contents of the accumuhttor by the umber stored ataddress 003.

M5 sTA 700 Store the contents oi the accumulator at the ad 7w plus themutants oi the Index Register.

046. INC 001 Increment the Index R tar by l.

47. C18 002 Compare the contents 0 the Index Register with the numberstored in location 002 which contains the number 48.

It the contents are unequal, take the next instruction; if equal, skip linstruction.

M8 J MP 04! Arrival at this point from the preceding com rlson meansthat the cycle count is not yet complete; therefore, jump to storagelocation 038 to beg n another cycfi D19. BIS (Ill Set Index Register to0.

" 0AA 201 Cldear gm acgrrmuhtor and add to the accumulator the numberstored at the address 201 plus the contents oi the In- 05L BUA 70oSubtract mm the accumulator the number stored at the address 700 plusthe contents of the Index Register.

062. STA son Store the contents or the accumulator at the address 800plus the contents of the Index Register.

053.. INC 001 Increment the Index R tar by l.

54.. (I5 002 Com re the contents the Index Registerwith the numberstored in location 002 which contains the number 48.

It t e contents are unequal, take the next instruction; if equal, skip linstruction.

065. J MP 050 Arrival at this point from the receding comparison meansthat the cycle count is not yet complete; therefore, jump to storagelocation 050 to b n another eye a.

050.. SIS (I!) Set Index R ister to 0.

057. PM! 800 Print on the rinter #1 the number stored at the address 800plus the contents of the Index Register.

058. INC (Ill Increment the Index It later by 1.

CIB 002 Compare the contents 0 the Index Register with the number storedin location 002 which contains the number 48.

I! the contents are unequal, talre the next instruction; 1! equal, skip1 instruction.

000.. I MP 0157 Arrival at this point from the receding com 11 meansthat the cycle count is not yet complete; therefore, jump to storagelocation 057 to n another eye e.

CB? 001 Increment the printing head y 1 column. 7 H V H V a m The 3r lnperformfii tlse It: The instruction DIA 001 causes the surn stored inthe E above propels is as fdlowa The instruction RCI 100 u cumulatzorI39 to be divided by 3 which is the contents of decoded in degrades ISQacts ovengoutrol line 11932 storage location 001. By dividing thecontents of the accumu' card 'F read out the 8" p lstor by 3, thegravitational value averaged over an interval 2T in; the gravity valuesalong the profile of row 8, FIG. 1. The i nbmi iaddressportionct'thisinstructiomdeoodedinaddressregisser I cu vetcontrol a w p he I w lat'glhitrmcgrusrrt 400stores the contents oftheaccumuconseeutive storage locations on magnetic drum 132. The V codeswill be stored in locations 100 to 149 since there are 49 The ndexregister is incr men ed by the instruction INC codes representing thegravitational values at each of the sta- 001', and a comparison is madewhich indicates the indexing tions A,8 to VVJ on FIG. 1. Similarly, thenext two insrmccycle is not complete. Therefore, the cycle is startedover lions RC1 200 and RCI 300 will cause the digital codes beginning atthe instruction CM 100 beginning at address representing gravitationalvalues along the rows 9 and 10, 014. However. during this cycle each ofthe addresses will be FIG. I, to be stored in consecutive storagelocations beginning incremented by the contents of the index registerwhich is l.

at eddre. 200 and address 300 respectively. In order to Therefore, thegravitational values stored at storage locations generate an averagedgravity profile over the smoothing interval 31, the irltructions atadthesses 0l3 through 021 are executed.

ml, 102 and 103 will be added and divided by 3 and these will be storedin storage location 401. in the next indexing cycle the s tents ot'storag e locations I02, I03 and 104 will be added. divided by 3 andstored in storage locations 402. The indexing cycles will continue untilall 49 ot the gravitational values along the row 8 of FIG. I have beenaveraged over the interval 2T. At this time the index register willcontain a 49 and an equal comparison will cause the computer to skip tothe instruction at address 022 which is SIS 000.

The same cycles described above will be repeated for the gravitationalvalues on the rows 9 and 10. These gravitational values will be averagedover the interval 21' as described above. In order to generatearea-gravity profiles by combining a plurality of the profiles averagedby the same smoothing interval, the instructions at addresses 040through 048 are executed.

The block of instnictions stored at addresses 040 through 048 causes thethree gravity profiles from the rows 8, 9 and 10. which have beenavenged over the interval 2T, to be added together and divided by 3 toproduce the average area profile represented as 2 T :-rmay) The averagedarea profile are called up from storage and subtracted from the values35 g(.r,y) which have previously been stored in consecutive storagelocations starting at address 200. This subtraction is perfonned by theinstructions at the addresses 049 through 055.

The results of this subtraction, representing the expression l' "l g(=yJ- M 2/) are stored in consecutive storage locations starting ataddress 800.

The values of 2 T 4" l m 10- m. y)

are printed out on a column of the moving chart by the instructions atthe addresses 056060.

Finally, the instruction CS? 001 increments the printing head to theright by 1 column so that during the next cycle of operation the values2 T will be printed in an adjacent column When the gravitational datafrom all of the stations on the map of FIG. I have been averaged on anarea basis and printed on the record 164, equal values on the chart canbe interconnected to form an equigravity map such as that shown in FIG.3.

Referring now to the flow sheet shown in FIG. la the gravity profileg(y,) which may be, for example, the gravity values along the line 20 inFIG. 1, is averaged over the smoothing interval IT as indicated at 201.Similarly, the gravity profiles g(y,) and g(y,), which may be a seriesof gravity values along lines parallel to and below the line 20 in FIG.I, are averaged over the same smoothing interval 21' as indicated at 202and 203. The smoothed gravity profiles g(.r,y),. g(.r,y and g(x,y) areaveraged as indicated at 204 to generate the average area value 2 T Inorder to accentuate the appearance of anomalies at a particular depth,the area gravity value is subtracted from the value g(.r,y as indicatedat 205.

5 To accentuate anomalies at a different depth, the area gravity value4T l' "'i 0( y) I0 is subtracted from the area gravity value asindicated at 206. The area gravity value 15 4T l' "l m. u)

is generated by averaging gravity profiles over the interval 41' asindicated at 207-209 and then averaging the smoothed profiles on an areabasis as indicated at 210.

The foregoing demonstrates the principles of the digital computerroutine which may be extended to include generating values whichaccentuate anomalies at differing depths as previously discussed.

Of course, it will be understood that various modifications may be madewithout departing from the principles of the invention. The appendedclaims are, therefore, intended to cover any such modifications withinthe true spirit and scope of the invention.

l. eTnethod for processing data representing physical properties of theearth including anomalies in a particular area comprising the followingsequential steps executed by an automatic computin apparatus:

generating signals representing smoothing data profiles 3088 lines ofsaid particular area, said smoothed profiles being smoothed by differingSmoothing intervals extending along said data profiles.

generating signals representing area-data values comprising thecombination of a plurality of the profiles smoothed by the samesmoothing intervals, and

generating signals representing subtracting an area-data value formed bycombined profiles smoothed by one smoothing interval from an area-datavalue formed by combined profiles smoothed by a different smoothinginterval to enhance the appearance of the anomalies on an area basis.

2. The method of claim 1 in which the step of generating signalsrepresenting said smoothed profiles comprises integrating with respectto distance along said data profiles,

and

algebraically adding together values from said integrated profilecorresponding with f g,( r+n T)dt f g,( tn T)dr where 3,") representsdata values along the x data profile where 07 represents one-half thesmoothing interval, and

t represents distance along said data profile to provide a resultantsum.

3. The method of operating a computing apparatus to treat gravityprofiles representing gravitational anomalies comprising the followingsequential steps executed by an automatic computing apparatus:

generating a plurality of transducible digital codes representingsmoothing gravity profiles g(x,y) over differing smoothing intervalsextending along each gravity profile,

generating transducible digital codes representing gravity profilessmoothed by the same smoothing interval and representing a plurality ofaveraged area-gravity values, and

generating transducible digital codes representing subtracting averagedarea values one from the other to generate difference area-gravityvalues thereby to enhance the appearance of anomalies on the separateseveral difference area-gravity values.

1. The method for processing data representing physical properties ofthe earth including anomalies in a particular area comprising thefollowing sequential steps executed by an automatic computing apparatus:generating signals representing smoothing data profiles across lines ofsaid particular area, said smoothed profiles being smoothed by differingsmoothing intervals extending along said data profiles, generatingsignals representing area-data values comprising the combination of aplurality of the profiles smoothed by the same smoothing intervals, andgenerating signals representing subtracting an area-data value formed bycombined profiles smoothed by one smoothing interval from an area-datavalue formed by combined profiles smoothed by a different smoothinginterval to enhance the appearance of the anomalies on an area basis. 2.The method of claim 1 in which the step of generating signalsrepresenting said smoothed profiles comprises integrating with respectto distance along said data profiles, and algebraically adding togethervalues from said integrated profile corresponding with gx(t+nT)dt-gx(t-nT)dt where gx(t) represents data values along the x data profilewhere nT represents one-half the smoothing interval, and t representsdistance along said data profile to provide a resultant sum.
 3. Themethod of operating a computing apparatus to treat gravity profilesrepresenting gravitational anomalies comprising the following sequentialsteps executed by an automatic computing apparatus: generating aplurality of transducible digital codes representing smoothing gravityprofiles g(x,y) over differing smoothing intervals extending along eachgravity profile, generating transducible digital codes representinggravity profiles smoothed by the same smoothing interval andrepresenting a plurality of averaged area-gravity values, and generatingtransducible digital codes representing subtracting averaged area valuesone from the other to generate difference area-gravity values thereby toenhance the appearance of anomalies on the separate several differencearea-gravity values.
 4. The method of operating a computing apparatusrecited in claim 3 in which said step of generating transducible digitalcodes representing averaged area-gravity values comprises averaging agroup of gravity profiles each of which is smoothed by the interval 2T,averaging A group of profiles each of which is smoothed by the interval4T and by further averaging other groups of smoothed gravity profiles,the profiles in each group each being smoothed by smoothing intervalsrepresented by 2nT where n is an integer and T is one-half the length ofthe smallest smoothing interval.
 5. The method of operating a computingapparatus recited in claim 4 wherein said step of generatingtransducible digital codes representing averaged area-gravity valuescomprises averaging 2n+1 of said profiles smoothed over the smoothinginterval 2nT to form the averaged area-gravity value and averaging 2n1+1 of said profiles smoothed over the interval 2n 1T to form theaveraged area-gravity value and said step of generating transducibledigital codes representing subtracting averaged area values comprisessubtracting the averaged area-gravity value from the averagedarea-gravity value to generate a plurality of difference values whichenhance the appearance of the anomalies in a given depth range.
 6. Themethod of operating a computing apparatus recited in claim 4 whereinsaid step of generating transducible digital codes representingarea-gravity values comprises averaging three of said profiles smoothedover the smoothing interval 2T to form the averaged area value andwherein said step of generating transducible digital codes representingsubtracting averaged area values comprises subtracting the averagedarea-gravity value from the gravity profile g(x,y) to compute adifference value on an area basis which enhances the appearance ofanomalies in one given depth range, wherein said step of generatingtransducible digital codes representing averaged area-gravity valuescomprises averaging five of said profiles smoothed over the smoothinginterval 4T averaged to form the averaged area-gravity value and whereinsaid step of generating transducible digital codes representingsubtracting averaged area values comprises subtracting the averagedarea-gravity value from the averaged area-gravity value to obtain adifference value on an area basis which enhances the appearance ofanomalies in a second given depth range, and wherein further differencevalues are obtained to enhance anomalies appearing in other depth rangesby repeating said step of generating transducible digital codesrepresenting averaged area-gravity values combining 2n+ 1 of saidprofiles smoothed over the smoothing interval 2nT to form the averagedarea-gravity value and combining 2n 1+1 of said profiles smoothed overthe interval 2(n-1)T to form the averaged area-gravity value and byrepeating said step of generating transducible digital codesrepresenting subtracting the averaged area-gravity value from theaveraged area-gravity value to obtain said difference values whichenhance the appearance of the anomalies in given ranges of depth.
 7. Themachine implemented method for automatically treating data representinga plurality of gravity profiles separated one from the other by adistance T and together coextensive with a mapped area which comprisesgenerating signals in said machine representing modified gravityprofiles in response to signals in said machine representing gravityvalues from each profile separated by the distance T wherein thegenerating step includes generating signals representing algebraicaddition together of said values in accordance with the expressiongx(t+T)dt- gx(t-T)dt where gx(t) represents gravity values along the xgravity profile, T represents one-half the distance of the smallestsmoothing operator, and t represents distance along said gravity profileto produce physical representations in said machine representing aresultant sum, modifying said sum by the factor (1/2T) further modifiedby division by the number of profiles which have been added together,generating signals in said machine representing subtracting saidmodified profiles averaged together with one smoothing interval fromother modified gravity profiles including a different smoothinginterval, and generating signals in said machine representing saidgravity values each separated from the other by the distance t forproduction of new gravity values in the same locations on the mappedarea.
 8. The method of operating a programmed computing apparatus totreat gravity information representing gravitational anomalies in aparticular area which comprises generating signals in said computingapparatus representing a plurality of gravity profiles derived from saidgravity information each of which represents said gravity informationacross a different section of said area, generating signals in saidcomputing apparatus representing smoothing each of said gravity profilesby differing smoothing intervals extending along said gravity profiles,generating signals in said computing apparatus representing averagingtogether groups of said smoothed gravity profiles, the gravity profilesin each group having been smoothed by the same smoothing interval, toobtain averaged area-gravity values, and generating signals in saidcomputing apparatus representing subtracting said averaged area valuesone from the other to generate difference area-gravity values thereby toenhance the appearance of anomalies on the separate several differencearea-gravity values.
 9. The method of automatically operating acomputing apparatus to treat gravity information to obtain an averagedarea-gravity value relative to a particular location x,y so thatgravitational anomalies represented by said information are enhancedcomprising the steps of, generating signals within said computingapparatus representing gravity profiles of said gravity informationacross a particular section, each of said gravity profiles representinggravity information along parallel lines spaced integral multiples of aninterval distance T from the location x,y for which the averagedarea-gravity value is to be obtained, generating signals within saidcomputing apparatus representing smoothing each of said gravity profilesto form a plurality of smoothed gravity profiles, smoothed by differingsmoothing intervals extending along said profiles, generating signalswithin said computing apparatus averaging together a group of smoothedgravity profiles each of which has been smoothed by a smoothing intervalwhich is an even multiple of the distance T to represent a plurality ofaveraged area-gravity values, an equal number of profiles in each groupbeing spaced on both sides of the location x,y by integral multiples ofsaid distance T with the furthermost spaced profile in each group beingspaced a distance from said location x,y corresponding with one-half thesmoothing interval used to smooth said profiles, and generating signalswithin said computing apparatus representing subtracting said averagedarea values one from the other to represent difference area-gravityvalues thereby to enhance the appearance of anomalies on the separateseveral difference area-gravity values.
 10. The method recited in claim9 wherein said step of generating signals within said computingapparatus representing smoothed gravity profiles comprises representingintegrating said gravity profiles with respect to distance, andalgebraically obtaining the difference between an integrated gravityprofile represenTed by the gx(t+nT)dt and gx(t-nT)dt where gx(t)represents gravity values along the x gravity profile, t representsdistance along said gravity profile and n is an integer.
 11. The methodrecited in claim 9 wherein said step of generating signals within saidcomputing apparatus representing said plurality of averaged gravityprofiles comprises averaging together the smoothed gravity profilepassing through the location x,y and an equal number of smoothed gravityprofiles on both sides of location x,y the total number of smoothedgravity profiles which are averaged being specified by 2n+1, and whereineach of the smoothed gravity profiles has been smoothed by an interval2nT where n is an integer.
 12. The method recited in claim 11 whereinsaid step of generating signals within said computing apparatusrepresents subtracting said area-gravity values comprises subtracting anarea-gravity value formed by averaging gravity profiles smoothed by theintegral 2nT from an area-gravity value formed by averaging gravityprofiles smoothed by the interval 2(n-1)T to form a differencearea-gravity value which accentuates anomalies in a particular depthrange.
 13. The computer performed method of automatically andsequentially processing data representing physical properties of theearth including anomalies in a particular area which comprisesconverting said data to first physical representations within saidcomputer representing data profiles across lines of said area,generating second physical representations within said computer fromsaid first physical representation representing smoothing each of saidprofiles by differing smoothing intervals extending along said profiles,generating third physical representations within said computer from saidsecond physical representation representing adding a plurality ofprofiles smoothed by the same sampling interval to represent a firstsum, generating fourth physical representations within said computerfrom said first and second physical representations representing addinga plurality of profiles smoothed by a different smoothing interval torepresent a second sum, and generating fifth physical representationswithin said computer from said third and fourth physical representationsrepresenting subtracting said first sum from said second sum to enhancethe appearance of an anomaly representing said physical properties ofthe earth.
 14. Apparatus for processing gravity profile datarepresenting gravitational anomalies of the earth in a particular areawhich have been converted to physical representations representinggravitational values including circuitry comprising an averaging meansfor generating from said gravity profile data first signals representinggravity profiles smoothed by differing smoothing intervals extendingalong said profiles, an adder means for generating second signals fromsaid first signals representing adding together a plurality of saidgravity profiles smoothed by a first smoothing interval to generate afirst sum, an adder means for generating third signals from said firstsignals representing adding together a plurality of said gravityprofiles smoothed by a second smoothing interval, which is differentfrom said first smoothing interval, to generate a second sum, and adifference means for generating fourth signals from said second signalsand said third signals representing subtracting said first sum from saidsecond sum to enhance the appearance of anomalies in the resultant.